The 2012 BMW 328i is the first example of the all-new 6th-generation 3 Series sedan (code name: F30) we've had in the shop.

It's hard to tell with the naked eye, but the footprint of BMW's volume seller has grown significantly. Longer overall by 4.3 inches, it now rides on a wheelbase that's 1.9 inches longer. And even though its overall width has shrunk by a scant 0.2 inches, the U.S.-spec 2012 328's tires have been spread farther apart by 1.2 inches up front and 2.3 inches out back. Despite all this, the curb weight of a 328i manual only increases by 44 pounds.

In CAFE terms, the footprint has been increased 5 percent, from 44.8 square feet to 46.9 square feet. That's interesting because cars with bigger footprints have less aggressive fuel economy increase targets. And the new CAFE standards only regulate the footprints you build in a given year, not the footprints you built last time out. At least in part, this size growth may be an example of strategic upsizing for CAFE purposes.

But such regulatory talk is boring. Let's see the metal.

Along the way you might want to open my walkaround of a 2009 BMW 3 Series in another window. That one was an M3, so you'll see more aluminum, but you can still see how the basic architecture differs...or doesn't.

Even though the detail dimensions are different, the basic 3 Series suspension philosophy remains. This is still a strut-based front suspension.

As before, this is a "dual link" strut, in that it uses two distinct links (green), each with their own ball joint, instead of a single lower control arm and one lower ball joint.

The front stabilizer bar is direct-acting via an elongated stabilizer link (yellow) that connects directly to the strut housing.

The key advantage of this arrangement is the ability to move the virtual steering pivot point outboard to a spot that would be physically impossible with a single ball joint. This in turn allows the engineers to reduce the scrub radius and do other cool things with steering geometry. Of course the "instantaneous virtual" intersection point shown above is constantly moving, so figuring it out properly is a bit more complicated than just overlaying a couple of yellow lines.

Pretty neat, huh?

Among all that aluminum there's a front suspension height sensor (green) and we can just see the bottom of the twin-tube front strut (yellow).

One of the "tells" that gives away the twin-tube strut is this (green) flattened section for tire clearance. And this mechanism (yellow) shows that this 3 Series is equipped with the "Adaptive M Sport" suspension with electronically controlled dampers. The height sensor we saw previously is one of several inputs that feed into the controlling ECU.

The 328i's brakes, meanwhile, are comprised of single-piston floaters (green) and ventilated rotors. One of the openings in the front grille (yellow) brings in cool air.

Peel back the diagonal hood seals on either side and you'll find a strut tower brace (yellow) that ties into the firewall.

Hard to tell what's going on in back from this angle. Nicely finished wheel well, though.

The rear of the new 3 Series is propped up by a 5-link multilink setup that's similar, but not identical, to last year's. It's almost impossible to see all five links in one shot, but we'll eventually catch up with all of them.

As we've seen many times before, the two upper links (green) approximate an upper A-arm. The forward-most of the two lower links (yellow) is visible, but the rearmost one is not because it's behind the shock. The slender link at the rear (orange) is the toe link.

From this vantage point we can see the missing link (yellow), a massive affair that also carries the spring and shock absorber. The toe link (green) we saw in the last shot sits just above it. Both of them have eccentric cams built into their inner attachment points; the lower one is for camber and the upper one is for toe.

This head-on view of the same links shows the eccentric cams a bit more clearly. It also shows us the motion ratio of the spring to be about 0.60-to-1 and that of the shock to be about 0.85-to-1, not unlike the outgoing generation.

The underneath view (my new favorite) shows just how the two lower links work together. None of this was all that visible until I first removed an aerodynamic cover that fastens to four tiny bolts that surround the spring pocket.

A smallish (but big enough) rear stabilizer bar (green) snakes between the upper links on the way to meet its own drop link.

That link is made of high-grade plastic and has ball joints on both ends. It attaches directly to the knuckle at a 1-to-1 motion ratio.
Right next door stands another twin-tube shock with electronically adjustable damping.

Wherever there are computer-controlled shocks there will also be suspension position sensors.

One thing was not mentioned here is that with the M-Sport suspension there is an additional sensor on the strut housing that is an accelerometer, it detects the rate of changes with which the suspension travels up and down (not to be confused with the height sensor).

All and all, I think a regular sport suspension equipped car with a nice set of lightweight wheels and tires (totaling ~40lb) will be a far better improvement to the car than an m-sport suspension setup.

One thing was not mentioned here is that with the M-Sport suspension there is an additional sensor on the strut housing that is an accelerometer, it detects the rate of changes with which the suspension travels up and down (not to be confused with the height sensor).

All and all, I think a regular sport suspension equipped car with a nice set of lightweight wheels and tires (totaling ~40lb) will be a far better improvement to the car than an m-sport suspension setup.

Basically I am saying that if given the choice of lightweight wheels/tires vs m-sport I would pick light weight. The effect of rotational mass on the car is far more pronounced than stationary weight at a rate of ~ 1 to 5 (varying based on what is happending with the car at the moment). Meaning that if you drop each corner by 13 lbs you will get the same effect as having ~200lbs lighter car.

The key advantage of this arrangement is the ability to move the virtual steering pivot point outboard to a spot that would be physically impossible with a single ball joint. This in turn allows the engineers to reduce the scrub radius and do other cool things with steering geometry.[/i]

Does anyone know what the actual scrub radius is on the F30 328i vs. 335i? Also, what "cool things" have the engineers done with the steering geometry in both cars?

Nice article ! The suspension is very similar to the e90 suspension. The e90 even has some links in the rear made from aluminium. But I suppose BMW chose steel on the F30 to help offset the extra front weight due to the bigger front overhang and maintain the 50/50 weight balance front/rear.

You can lower the unsprung weight by 10lbs per corner by getting some well-chosen non-runflat tires (like Continental DW for summer or Continental DWS for all-season - they are both very light) and exchanging the wheels with 20lbs semi-forged wheels which can be had for about $900 a set and are quite strong. This way a wheel/tire combo will weight like 43lbs, as opposed to 53lbs. With this kind of setup I would bet you will gain like 0.4s in the 0-62mph sprint.

Stamped steel rear suspension components? I could have swore that everything on the E90/E92 (non-m3) was aluminum.

yup, aluminum cast is far more expensive. I personally look at it as step backwards. That said it all depends if the new steel components are actually lighter and/or stronger because of its hollow design.